# know inside and out

idiom

Source: https://englishreference.com/idiom/know-inside-and-out
Updated: 2026-08-10

## Meaning

To know (something or someone) very thoroughly.

## Examples

- He knows the city streets inside and out.
- After working at the company for ten years, she knows the software inside and out.
- The seasoned detective claimed he knew the criminal's habits inside and out, allowing him to predict the next move with ease.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.